This section provides background information related to the present disclosure which is not necessarily prior art.
In view of increased consumer demand for motor vehicles equipped with advanced comfort and convenience features, many modern motor vehicles are now provided with passive entry systems to permit locking and release of closure panels (i.e., doors, tailgates, liftgates and decklids) without use of a traditional key-type entry system. In this regard, some popular features now available with vehicle latch systems include power locking/unlocking, power release and power cinching. These “powered” features are provided by a latch assembly mounted to the closure panel and which includes a ratchet and pawl type of latching mechanism controlled via at least one electric actuator. Typically, the closure panel is held in a closed position by virtue of the ratchet being positioned in a striker capture position to releaseably retain a striker that is mounted to a structural portion of the vehicle. The ratchet is held in its striker capture position by the pawl engaging the ratchet in a ratchet holding position. In most ratchet and pawl type of latching mechanisms, the pawl is operable in its ratchet holding position to retain the ratchet in one of an initial or soft close striker capture position and a primary or hard close striker capture position. Latch assemblies providing a power cinching feature are typically equipped with a cinching mechanism operated by an electric actuator. Commonly, the cinching mechanism is directly connected to the ratchet and, when actuated, is operable for moving the ratchet from its initial striker capture position into its primary striker capture position, thereby cinching the closure panel in its closed position. To subsequently release the closure panel from its closed position, a release mechanism is actuated for moving the pawl from its ratchet holding position into a ratchet release position, whereby a ratchet biasing arrangement forcibly pivots the ratchet from its primary striker capture position into a striker release position so as to release the striker. In latch assemblies providing a power release feature, the release mechanism is controlled by an electric actuator. A common electric actuator or separate electric actuators can be used in associated with the power release and power cinching features. However, the power release feature is typically independent from the power cinch feature. As an alternative, it is also known to employ a double pawl type of latching mechanism to reduce the release effort required for the electric actuator to release the latching mechanism.
In most latch assemblies equipped with a power cinching feature, the cinching mechanism is normally maintained in a non-actuated or “stand-by” condition and is only shifted into an actuated condition once the sensors indicate that the ratchet is located in its initial striker capture position. Following completion of the cinching operation, when the sensors indicate that the ratchet is located in its primary striker capture position, the cinching mechanism must be “reset”, that is returned to its stand-by condition, to permit subsequent uninhibited movement of the ratchet to its striker release position via actuation of the release mechanism. If the closure panel is initially closed with a sufficient closing force to locate the ratchet in its primary striker capture position, then the cinching operation is bypassed and the cinching mechanism is retained in its stand-by condition. One example of a power cinching latch assembly is disclosed in U.S. Pat. No. 6,341,448 as having a cable-type cinching mechanism.
To ensure that precipitation and road debris do not enter the vehicle, virtually all vehicle closure panels are equipped with weather seals around their peripheral edge and which are configured to seal against a mating surface of the vehicle body surrounding the closure opening. These weather seals also function to reduce wind noise. The seals are typically made from an elastomeric material and are configured to compress upon closing the closure panel by virtue of the latch assembly. As is recognized, increasing the compressive clamping force applied to the weather seals provides improved noise reduction within the passenger compartment. As will be appreciated, with the weather seals held in a highly compressed condition, they tend to force the closure panel toward its open position and this “opening” force is resisted by the pawl and ratchet latching mechanism of the power latch assembly. Because the seal loads exerted on the latching mechanism are increased, the forces required to release the latching mechanism are also increased which, in turn, impacts the size and power requirements of the electric actuator. Further, an audible “pop” sound is sometimes generated following actuation of the electric actuator during a power release operation due to the quick release of the seal loads while the ratchet of the latching mechanism is forcibly driven from its primary striker capture position into its striker release position.
To address this dichotomy between high seal loads and low release efforts, it is known to provide an arrangement for controllably releasing the seal loading in coordination with release of the latching mechanism. For example, European Publication No. EP1176273 discloses a single ratchet/double pawl type of power-operated latching mechanism that is configured to provide a progressive releasing of the ratchet for reducing noise associated with its release. In addition, European Publication EP0978609 utilizes an eccentric mechanism in association with a single pawl latching mechanism to reduce seal loads prior to release of the ratchet.
While current power latch assemblies are sufficient to meet regulatory requirements and provide enhanced comfort and convenience, a need still exists to advance the technology and provide alternative power latch assemblies and arrangements that address and overcome at least some of the known shortcomings.